Particulate contamination is an important problem in semiconductor manufacturing. Particles create defects in integrated circuits thereby lowering process yields and increasing cost. Particle contamination is even more important as device dimensions become smaller. For example, a given particle size that may not have caused a defect on a 1.0 μm feature may destroy a device as that feature shrinks to 0.50 μm or below.
Many lithography processes use a top coat (TC) such as an antireflection coating (ARC) on top of a resist film. Particles deposited on the top coat create defects in the final image. Therefore, the lithography process typically includes a preliminarily cleaning of the wafer to remove unwanted particles. A variety of techniques have been proposed and implemented in the prior art in order to clean semiconductor wafers.
Some conventional cleaning methods include rinsing or spraying a cleaning solution on a wafer surface. However, as a liquid flows over the surface, there is a convection boundary layer wherein the convection velocity ranges from zero at the surface to the mainstream velocity in the bulk liquid. Because the convection velocity is almost zero near the surface, rinsing or spraying is often ineffective in dislodging particles attached to the surface or trapped in recesses. To overcome this problem, other conventional cleaning methods use ultrasonic vibrations, which more effectively clean the wafer surface. However, these methods have drawbacks as well.
Many conventional methods introduce new solvents into the lithography process. These new solvents, in turn, raise additional toxic or environmental concerns in a process already burned with such problems. Other conventional cleaning methods employ environmentally friendly solvents, such as liquid nitrogen or an argon cryogenic aerosol, but even these solvents require specialized and expensive handling equipment.
In light of problems such as these, there remains a need for improved methods for removing particulate contamination in semiconductor manufacturing.